textproduct: Albany

WHAT HAS CHANGED

The Winter Weather Advisory was broken into 2 sections. The southern Herkimer and Fulton Counties segment will begin still at 00Z/7 pm with snow totals of 3 to 7 inches into Saturday evening. The northern Saratoga, Taconics, Dutchess County, Litchfield Hills, Berkshires and southern VT segment will now begin at midnight and run until 1 am Sunday for 3 to 6 inches of snow with up to 8 inches locally over the southern Greens.

KEY MESSAGES

1) Slippery travel conditions across eastern New York and western New England tonight through Saturday as areas of snow produce light to moderate snowfall accumulations.

2) The potential for additional light snow, mainly for portions of the Mid-Hudson Valley, Taconics and western New England, increases the potential for another brief period of slippery travel conditions Sunday evening/Sunday night.

3) The potential for moderate to potentially heavy lake effect snow is increasing for portions of the Southwest Adirondacks Monday evening through Wednesday but little impacts are anticipated given the highly localized area that snow will fall in.

4) Below normal temperatures are largely expected for next week with breezy winds making for biter cold conditions at times.

DISCUSSION

KEY MESSAGE 1...

A low pressure system will track into the northern Great Lakes this evening from the Upper Midwest beneath a northern-stream shortwave trough. A deepening, positively-tilted trough will simultaneously dig south and east across the Midwest, increasing cyclonic vorticity advection across the region as deep southwesterly flow supplies moisture into the favored left exit region of the upper-level jet. Additionally, warm air advection also promoted by southerly flow will allow areas of snow to develop beginning tonight across eastern New York and western New England.

Overall moisture supply is limited with this system as the steep, positive tilt of the trough upstream cuts off moisture transport into the region. Therefore, overall snowfall rates are anticipated to be light for most areas. An overall lack of strong forcing, too will limit the magnitude of snowfall rates tonight through tomorrow for most areas. However, upslope flow will greatly influence snowfall in portions of the Mohawk Valley, Southern Adirondacks, Lake George-Saratoga Region, Taconics, Southern Vermont, Berkshires, and Litchfield Hills where moderate snowfall accumulations are anticipated. Portions of the Eastern Catskills and Mid-Hudson Valley, too, could have localized moderate snowfall amounts due to the stronger area of warm air advection that is anticipated to cross through there later tonight. Overall snowfall amounts will range from about 3 to 6 inches with locally higher totals around 8 inches in isolated, higher elevations of the Southern Greens.

KEY MESSAGE 2...

A fairly potent coastal storm continues to be feature of interest for Sunday afternoon into Sunday night. Over the last several days, deterministic models have been varied in their portrayal of the track of this system with some runs indicating a more east-northeast progression that would keep it out of reach of our area and others resolving more of a north-northeast track that may allow its deformation zone to scrape at least our far-southeast zones. That said, ensembles have been fairly consistent with favoring the east-northeast track which would significantly limit the impact, if any, the storm has on our area.

After close consideration of all the data and extensive collaboration with our neighboring Weather Forecast Offices, the general, high-confidence consensus sides with the east-northeast track that will push the storm farther off shore and subsequently result in little to no impacts locally. While the anticipated ridge over the central Atlantic will amplify Saturday night into Sunday, it won't be to a sufficient extent to steer the low closer to the coast. Said amplification will also take place too far to the northeast to have much steering control over the developing low. Additionally, there is a lack of phasing of several embedded shortwaves within the mean trough aloft that the low is associated with. This lack of phasing will also favor pushing the low farther away from the coast and subsequently farther from our area.

That said, we chose to implement the mention of this system back into the key messages because, despite the consensus of the farther east track, there is still some hint that the large deformation precipitation zone associated with this system could sneak into some of our southeastern areas. In fact, the National Blend of Models (NBM) PoPs increased for portions of the Mid-Hudson Valley, Taconics, and western New England from previous runs. Now, it's important to note that these PoPs only span the slight chance to chance categories with very little in the way of snowfall in these areas during the Sunday afternoon through Sunday night timeframe (less than an inch). But we felt it important to at least message this change from previous forecast iterations. We will continue to maintain a close eye on trends to catch and adjust the forecast to any low probability, "surprise" situations, but maintain that this will likely be a non-eventful end of the weekend for eastern New York and western New England.

KEY MESSAGE 3...

Medium-range models favor the development of at least one primary lake effect snow band off Lake Ontario in the wake of a potent cold front Monday night. As the passage of this front is closely followed by the passage of an upper-low overhead, cyclonic flow will promote the advection of moisture off the lake and requisite ascent to support this outcome. While exact snowfall totals are not yet certain, the latest run of the NBM has 30-60% probabilities for at least 7" of snow (Lake Effect Snow Warning Criteria) over a 72 hour period in northern Herkimer County. The probabilities for at least 4" of snow (Advisory Criteria) are even higher and more spatially extensive across northern Herkimer and northwest Hamilton County at 30 to nearly 90%. Therefore, at this time, we can say that there is at least moderate confidence in Advisory- level snowfall for portions of the Southwest Adirondacks Monday night through Wednesday, but the uncertain details of exact timing, band placement, and snowfall totals warrant the lack of high confidence at this point. That said, with this being such a localized area as it is, there will be few, if any, impacts or threats to life and property.

KEY MESSAGE 4...

Confidence continues to increase in temperatures falling below normal for much of next week as latest ensembles indicate anomalous troughing at least through the first half of the week. In fact, the latest NAEFs indicates upper-level temperatures (at the 500, 700 and 850 mb levels) reaching as many as 2 to 2.5 STDEVs below normal Tuesday and Wednesday with Thursday and Friday moderating slightly into the 1 to 1.5 STDEVs below normal level. This will translate to surface temperatures that are anywhere from about 0.5 to 1.5 STDEVs below normal and high temperatures that largely span the tens and 20s. To make conditions feel chillier, periods of elevated winds will also accompany these temperatures and increase the potential for Cold Weather Advisories to be issued. At this time, however, there is low confidence in whether these headlines will actually be needed and for what day. We will continue to closely monitor trends over the coming days and adjust the forecast where necessary.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

VFR conditions begin the TAF cycle for KGFL/KALB/KPOU/KPSF, but mid and high clouds will quickly be increasing ahead a low pressure system approaching from the Great Lakes Region and its warm front. Light snow will move in from the west/southwest to the north/northeast across the TAF sites between 04Z-08Z/Sat with MVFR/IFR conditions occurring. Vsbys will be in the 1-2SM range with cigs 1-3 kft AGL. Some LIFR conditions in terms of vsbys may occur for KALB/KPSF/KPOU between 12Z-20Z/SAT with cigs falling into the IFR levels at KPSF. The snow will begin to taper off between 19Z-21Z/Sat with MVFR/low VFR conditions returning, though some lingering scattered snow showers are possible, so PROB30 groups were used at the end of the TAF cycle for most of the TAF sites.

The winds will be light to calm early tonight and then will be south to southeast at 7 KT or less overnight through much of the morning. The winds will veer to the south to southwest in the afternoon at less than 10 KT. LLWS was used for KPOU/KPSF between 03Z-06Z/Sat until 09Z-13Z/Sat as the 2 kft AGL winds increase to 30-35 KT and the sfc winds are 5 KT or less.

Outlook...

Saturday Night: No Operational Impact. NO SIG WX. Sunday: Moderate Operational Impact. Chance of SHRA...SHSN. Sunday Night: No Operational Impact. NO SIG WX. Martin Luther King Jr Day: Low Operational Impact. Breezy. NO SIG WX. Monday Night: Low Operational Impact. Breezy. NO SIG WX. Tuesday: Low Operational Impact. Breezy. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Low Operational Impact. Slight Chance of SHSN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Winter Weather Advisory from midnight tonight to 1 AM EST Sunday for CTZ001. NY...Winter Weather Advisory from midnight tonight to 1 AM EST Sunday for NYZ041-054-061-065-066-084. Winter Weather Advisory until 1 AM EST Sunday for NYZ038-039- 082. MA...Winter Weather Advisory from midnight tonight to 1 AM EST Sunday for MAZ001-025. VT...Winter Weather Advisory from midnight tonight to 1 AM EST Sunday for VTZ013>015.